A control circuit includes: an input terminal for receiving an input AC voltage; a voltage decreasing unit for decreasing the input AC voltage; an A-D converter for converting the decreasing AC voltage to a DC voltage; a driving unit for receiving the DC voltage and to driving a motor, a detecting unit for detecting the DC voltage; and a current shunt unit configured to be conductive to lower the DC voltage at the output terminal of the A-D converter to a voltage which is less than a threshold voltage when the detecting signal indicates that the detected DC voltage exceeds the threshold value. A motor device includes the control circuit and a motor.